Portable Stereo Mic Preamp

Hi,

I'm a real newbie in DIY, but I'd like to make a portable stereo mic pre to feed my little Nagra ARES M Recorder with a Rode NT4. Actually, I wouldn't need a 48v phtantom supply, since the Nt4 works with a 9v batterie. But it can be usefull if I'd like to use other condenser mics in the future.

A friend of mine build a rackmounted green mic pre and told me it could do the job in a portable way. I found this pre really good. But I also see this one: http://www.celestial.com.au/~rosswood/diy/dualmicpre/dualmicpre.htm. Which one do you prefer and would you advice me?

I know that the mic pre could be fed with four 9v batteries and the most important question for me at the moment is to know how long it could last with it. Do you know, perhaps, other types of battery that would work better?

Thanks for your respones,

Chears,

Julien

The reasoning for the above project was simplicity and ease of component avalibility ... at the time ... and success of the project even for a beginner.

Most Mic-pres will probably work with 4 x 9volt batteries to make +/-18volts

How long it will last depend on many things,
the chosen batteries
idle currents for the Mic-pre
Load on the Mic-pre from the next stage
and more

It is very possible to make Mic-pres using descrete components to minimise the energy waistage ... or to use low power IC's
... also possible is to use a single battery and add a DC to DC convertey to make the rail or rails required
... like most of the News gathering gear (ENG) out there ... the Nagra


both the SSM2017/2019 OR the GreenMk1 are great choices for a first time portable Mic-pre.

the first question to answer could be
how much gain do you think you might need ??
for loud News stuff either is good
for Drama and natural sound I might swing to the Green
for higher gains the Green might sound better but the SSM2019 might be slightly quieter ... ?

simplicity go the chip ... nah go the Green

:shock:

:roll:


see ... I'm no help at all !!!
shut up Kev
:razz:

Are there any Class D mic pre designs out there? I'm sure I saw one website with a design, but have lost the link. Class D would be the most efficent for battery powered operation, but I'm not sure about any sound quality issues?

Hi julio,

I'm actually thinking about create a project like yours...

I created a post on a portable preamp some days ago...


http://www.groupdiy.com/index.php?topic=17807&highlight=

I think that the green preamp is good solution but the hardest thing is to find a good solution for the Power.

I think about use Nimh battery like there are in some broadcast Camera etc...

but I don't know how create a 48 Volt for phantom...

On SQN 4s you can have 48 Volt with only 12 volt battery, how is it possible!!

with charge bumper?

So any idea with a portable power supply are welcome :grin:

Julien, here is a thread on a stereo mic pre that I made.
It is portable, two nine volts, which lasted a whole three day weekend of use.
It is a no frills amp, no tone control, phase reverse, very simple, took me two days.

One side is for a Piezo pickup, the other is for your typical mic.

The quad opamp is enough stages for a one chip solution.

The mic side has a transformer input.

http://www.groupdiy.com/index.php?topic=15340&postdays=0&postorder=asc&start=0

so CJ, how does it sound?

It worked great!
No hum oncce I was out in the sticks.
Tons of gain, kind of the straight wire apporoach, low distortion chip.
I could get an SM 57 to feed back while it was down in the mine shaft 20 feet, and with a blanket over the entrance to muffle outside sound.
This was close to max gain, so perfect pot in there.
The Piezo section worked great also, the guys were right, you get a nasty sound when the piezo coax gets shaken around a lot.

Hello,

I read your thread about the mic pre you made. But although I think it's a good one, I think I'll choose the green as I already know how it sounds and because my friend knows how to build that.

I was quite busy the last weeks so I couldn't reply. But I made searches on the web and though about 2 solutions for the powering:
- use 2 batteries, used in model building for exemple( like this) in serie to have 19,22V and use this kind of schema to have +19,2V and -19,2V
.

or
- use just one batterie (probably the sameas for the firt solution) and use this dc-dc converter.This dc-dc converter is, I hope, a good choice because it can be used with 9v in and can have an output current of 500ma. According to Peter Cornell, each green pre draws 100ma in the worst case and someone said to me that the converter draws a little to but I couldn't find how much on the tech sheet.

Don't know which solution you find the best but I would prefer the second one for many reasons:
- It would take less space
- the converter would probably permit to have a more constant Voltage that is a good point as batteries drop voltage in use.
- price would probably be equivalent. For the first solution I would need 2 batterie loaders or wait twice the time for the load. And batteries aren't eternal: for the long time, the second solution would then be cheaper.
- about the autonomie, with the batterie I mentionned, It can last 6h, may be a little less if the dc-dc converter draws current. For me it would be enough. And I saw other batteries with more capacity.

What do you think?

I also would like to know if someone knows a way to control batterie level and to control the audio level with just one or two leds, so I could use the V9 PCB to gain space.

Do you think it would be possible to use just one knob for the level as I would mostly use it for stereo recording. If yes how?

Thnak a lot for your help!

SQN-3 Type M Battery powered location microphone amplifier and mixer:

http://twin-x.com/groupdiy/albums/userpics/SQN-3_type_M.pdf

Jakob E.

For my portable preamp I use a dc-dc converter like this (but with 4,5V-9V input):



And a simple 15V multiplier to make a 48V phantom power:



For battery (akku 6..7x 1,2V) supply, the best is TRACO POWER TEN 3-0522 or TEN 3-0523:

http://dsb.tracopower.com/upload/DSBUserFile/CPN_TracoPower/0_ten3.pdf

Have anyone other schematics like SQN? Mybe portable SHURE FP23, FP33 or Sound Devices?

Best Regards,
TB

Hey Julio,

Did you ever finished this project?